In European Patent EP 0 902 458 A2 a metal halide reflector lamp is shown comprising an outer envelope formed as a reflector with a neck portion and a base. A light transmitting cover in the form of a lens is connected along its circumference to an outer edge of the reflector, whereby reflector, base and cover are shaped generally rotationally symmetrical around a longitudinal axis. A light capsule or an arc tube, resp., having pinch seals at its ends and being surrounded by a shield formed as a tubular envelope and being arranged in the reflector within the shield by means of a first and a second electric lead. The first lead is at a first end of the capsule adjacent the base, and the second lead is installed on the outside of the shield and is introduced into the other end of the shield opposite the cover adjacent the second end of the capsule with both leads being sealed in the pinch seal adjacent the base. The reflector lamp shown in EP 0 902 458 A2 has a melting-in of the tubular envelope of the shield in the base area such that the two leads emerging from the base area are sealed into this pinch seal-like melting-in from which they exit in order to enter into pinch seals at opposite ends of the capsule. The shield thereby provides a so-called burst protection which protects the environment as against shards of a capsule which could explode possibly sometimes.
This known shield closed all around can be filled with a protective gas like nitrogen in order to protect from oxidation, at temperatures above 400 degrees Celsius, the welding between the respective lead-in and the respective sealed-in foil made from molybdenum which is necessary when quartz is used fox the capsule. It is known that sealings of lead-ins within quartz glass are not gas-tight because the thermal expansion coefficients are too different. The known shield as such, however, does not need any foils melted in because aluminum silicate glass is used for the shield, the thermal expansion coefficient of which corresponds essentially to that of the material of the lead-ins.
Even if this known structure is relatively compact already, the presence of a melt-in of the leads into the pinch seal-like end of the shield opposite the base and the use of protective gas constitutes a remarkable manufactural-technical expenditure on the one hand, on the other hand such melt-in makes the shield longer and by this enlarges the reflector lamp in the direction of its longitudinal axis.
With the reflector lamp known from WO 96/27205 A1 the first as well as the second lead-in are installed within the shield and exit from the shield at the side of the base, whereby a sealing consisting of curable cement is present between the shield and the lead-ins which is to be regarded as an additional expenditure the same way as melt-in which is for granting a hermetic sealing of the shield.
Finally the EP 0 560 936 B1 teaches a reflector lamp with a cylindrical shield which is retained by special clips which at least partially grip around the circumference of the shield at its two ends. The clips form part of a separate maintenance structure for the shield which comprises a holding web between the two clips and a special holding ring for the holding web in the base area of the lamp. This complicated maintenance structure for the shield forms a special expenditure.